Tapping the Oceans Mineral Wealth With Deep Sea Mining

No one knows how many hydrothermal vent sites are in the oceans, but there is a best guess. Amazingly, when scientists who have studied different parts of the ridge system compared notes at the April WHOI conference, they realized they were all coming up with the same distance between known, large active vent sites: 100 kilometers. If those numbers hold true, about 600 districts spewing metal-rich fluids and potentially holding sulfide deposits may decorate the mid-ocean ridge. Nautilus Minerals estimated in a September 2009 corporate presentation that "thousands of underwater sulphide systems exist," and "if only half of underwater systems are geographically viable, seafloor production would represent several billion tons of copper per annum." _Minerals from the Seafloor

Earth's seafloors are loaded with mineral wealth. Humans have just begun to learn to tap into the huge reserves of deep sea oil and natural gas. And seafloor methane clathrate reserves may be more than twice as abundant than all other forms of hydrocarbon deposits combined. Seafloor coal deposits are likewise huge beyond previous calculations.

But beyond hydrocarbon energy wealth, the ocean floors are rich with other minerals. From precious metals to uranium to large deposits of copper, zinc, iron, sulfur and more -- the oceans are likely to be Earth's richest repository of minerals. All we need to do is to learn how to get them safely and responsibly. In a review paper published June 23 online in the journal Mineralium Deposita, Cathles, Cornell professor of earth and atmospheric sciences, writes that while land-based deposits may be a dwindling source of valuable minerals, deposits on the ocean floor could power humanity for centuries.

The minerals, including sulfur, copper, zinc, iron and precious metals, are contained in volcanogenic massive sulfide (VMS) deposits that form on the ocean floor where tectonic plates pull apart and allow magma (molten rock) to invade the Earth's 3.7-mile- (6 kilometer-) thick crust. The magma heats seawater to 662 degrees Fahrenheit (350 degrees Celsius) and moves it through the ocean crust via convection; and the seawater deposits the minerals where it discharges along the ridge axis.

...If just 3 percent of the dissolved minerals precipitate -- an estimate based on earlier studies -- the ocean floor would hold reserves vastly greater than those on land, Cathles said.

In the case of copper -- a key component in construction, power generation and transmission, industrial machinery, transportation, electronics, plumbing, heating and cooling systems, telecommunications and more -- calculations show that just half of the total accumulated amount could be enough to bring the world's growing population up to a modern standard of living and maintain it for centuries.

"I think there's a good chance that it's a lot more than 3 percent," Cathles said. "But even just taking 3 percent, if you calculate how long the copper on the ocean floor would last, just half of it could last humanity 50 centuries or more. _RD

New Zealanders have begun exploring the mineral riches near local undersea volcanoes. And the Aussies have begun installing deep sea observatories to compile records of what is happening along deep sea vents -- where most metals tend to come up. US institutions are likewise beginning to map undersea resources.

Nautilus Minerals (see image at top) is already bringing deep sea minerals to market. Bluewater Metals Ltd. is another ambitious company eager to jump into the deep sea gold rush.

Little by little, mining companies are working their way through the international laws, committees, and bureaucracies in order to try out some of the advanced undersea technologies that are being developed.

Remotely piloted prospecting robots will be followed by autonomous robot prospectors and miners. Semi-permanent seafloor installations -- perhaps supervised by station-keeping manned submarines overhead -- are likely to evolve if the promise of the resource proves out. Ships are subject to surface storms, but submarines -- particularly nuclear submarines -- can stay submerged below surface turbulence and maintain data communication with equipment on the seafloor.

Deep sea robotic submersibles have come a long way since the early, heady days of speculation about deep sea mineral resources. If the mining companies currently pushing to get a hand in the game can exploit the resource cleanly and responsibly, this may be the beginning of the era of deep sea resources.